Bit of a chump, but sound (3)

I believe the answer is:
hum
'sound' is the definition.
(humming is a kind of sounding)
'bit of a chump but' is the wordplay.
'bit of' says the answer is hidden in the clue.
'HUM' can be found hidden inside 'chump but'.
(Other definitions for hum that I've seen before include "Sound (of business?)" , "Stench" , "Sing like a bee?" , "Reek" , "Make musical sound with closed lips" .)